Atomredzoloto, Moscow, Russia:

I. N. Solodov, Director of Innovation and Technological Advance Programs, Doctor of Geological and Mineralogical Sciences, INSolodov@armz.ru

Dalur develops geologically and hydrogeologically similar uranium deposits Dolmatovskoe, Khokhlovskoe and Dobrovolnoe in the Kurgan Region. In 2020 at Dobrovolnoe deposit, geological exploration was completed, and an in situ leach testing ground construction was started. The activities included geochemical research aimed to analyze safety of groundwater from radioactive pollution. The implemented research proved geological inaccessibility and natural geochemical protection of groundwater from a deep (550–600 m) pollution source generated in the course of in situ sulfuric acid leach of hydrogenous uranium at Dobrovolnoe deposit. The methods of groundwater protection from pollution using full-safe design of process boreholes with casing made of unplasticized polyvinyl chloride resin. Natural groundwater at hydrogenous uranium deposits are initially polluted with radioactive decomposition products (210Po, 210Pb, 226Ra, 227Ac, 230Th, 232Th) and stable components associated with uranium (hydrogen sulfide, selenium, arsenic, molybdenum, vanadium, bromine, fluorine, iron, manganese and chromium), and are therefore unsuitable for drinking and for domestic / industrial water supply. In situ leach method removes radioactivity by means of extraction of the long-living radioactivity source, namely, uranium which has a half-life period of 4.6 billion years. Low groundwater flow velocity in the ore-bearing middle – and upper Jurassic aquifer prevents from largescale pollution of groundwater (geological inaccessibility). The upper-lying impervious stratum with a very low cross-flow index of 10^–5–10^–7 day^–1 impedes flow of manmade water in the upper-lying aquifers (geological inaccessibility). In in situ leach the aquifers are artificially introduced with sulfate, nitrate and ammonium, the other petrogenic components extracted from rocks are given back to rock mass after auto-purification.

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